All over Ireland and across the world, family secrets are being revealed for the first time because of commercial DNA tests.
Whether by accident, through mere curiosity or as part of deliberate and painstaking detective work, individuals are finding out about a hidden biological parent or an unknown sibling.
They are discovering affairs and liaisons that were covered up for decades, and the results are often painful, but enlightening. Siblings such as the abandoned babies Helen Ward and David McBride, whose story was told in these pages this month, are suddenly united.
In some ways, the process of doing a DNA test seems simple. In return for a fee of less than €100, a company such as Ancestry or 23andMe will send you a test tube for you to spit in and send back for analysis.
Weeks later, reams of information come back, showing up relatives who have also given DNA samples.
Dolores Quinlan, a psychotherapist who herself found her mother through DNA and helps adoptees who are going through the process, says: "People give DNA tests as Christmas presents, but they should come with a government health warning.
"People might do the test for the craic, and they may get back a chart showing how Irish they are," she explains. "People can keep their information public or private, but many don't know that, and they leave their information on the database, where other DNA samples will be automatically linked with their sample if they match - including those of future DNA contributors.
"All of a sudden, they are contacted by someone who is a daughter of the husband from a previous relationship that they never even knew about. The husband might not even have known that their ex-girlfriend got pregnant and had a baby. Or else it could be a half-brother or sister that suddenly contacts you."
The State may be notoriously reluctant to release adoption records, but the emergence of relatively cheap DIY databases such as Ancestry has driven a coach and horses through that cloud of bureaucratic secrecy.
Libby Copeland, the American author who describes this changing environment in her book The Lost Family, says: "We are in a profound moment of historical reconciliation. This is the moment when everything comes out and everybody has to talk about it.
"There are hundreds of thousands of difficult conversations happening all across the world. In many families, that will be a good thing, but there is no denying the difficulty, and in some cases trauma."
The secrets that continue to emerge are all the more numerous in Ireland, where unmarried mothers were treated as "fallen women" in past decades, according to genetic genealogist Maurice Gleeson.
Children were spirited away, but thanks to DNA tracing, they are suddenly reappearing.
In many cases, such as that of Dolores Quinlan, they were adopted illegally with false birth records, and may only have discovered well into middle age that the parents they grew up with were not their biological mother and father.
It is not just the children of unmarried mothers whose true identities have been revealed. Sperm donors, who thought they were involved in conceiving babies on condition of anonymity, are suddenly having their identities uncovered through DNA tests carried out by their children.
For the West Cork artist Anne Crossey, the search for the identity of her father was a long and tortuous one, and there is still an element of mystery about how exactly she was conceived.
Some years ago, her mother revealed to her that she was conceived from a sperm donor in the 1970s, when the parents she grew up with were living in South Africa.
Her mother said she was told at the time of the conception that the donor was a medical student, but she was later informed that the doctor who organised the procedure had supplied the sperm himself.
Dr Norman "Tony" Walker, whose identity was later publicised, had treated hundreds of women, and used his own sperm in many cases.
Crossey, now 45 and living near Skibbereen, told Review this week how she faced the likelihood that she had many siblings. It could be dozens or even hundreds.
By reaching out to these potential brothers and sisters online, she was able to make contact with a group of them and they planned to meet in Australia. Beforehand, they decided to do DNA tests, with the common assumption Walker was their natural father. Crossey faced another shock in her quest for details of her paternity.
The tests showed that the rest of the group were indeed Walker's children, but her test showed she had a different father.
She wondered whether her genetic father was another sperm donor at the same clinic. "I was gutted to find out that I wasn't related to the others in the group," she says.
Crossey had to resume her DNA search.
"It was like trying to find a needle in a haystack, because I only had fourth and fifth cousin matches that came up after I did a test," she says. "What is happening now is that the technology is coming together between those who have made family trees and DNA tests."
By tracing back through common ancestors, she found four or five candidates who could be a close relative. She was able to rule out three of them through further DNA tests.
"I was ready to give up when I tried the last one, and it came back that this man was my half-brother," she says.
She discovered that she had three half-brothers, who lived in South Africa, and this year she met two of them. She found out that her biological father had been an engineer, who lived near her family in Durban. He died in the early 1980s.
The mystery did not end there. It is unclear exactly how this man became her father.
"I don't know if he was really a donor - whether the doctor used his sperm without him knowing, or if he voluntarily did it. Or he could even have had a relationship with my mother. My mum was a very attractive woman and my parents lived nearby."
Crossey says it was a huge relief to find out who her father was: "It's very stressful not knowing where you come from and not having an anchor. All I ever wanted were brothers and sisters, having grown up as an only child."
It appears that most people who use the DNA kits that have surged in popularity in recent years are not trying to trace a direct relative.
Maurice Gleeson, the genetic genealogist, says surveys suggest 60pc want to find out their ethnic background, 25pc are interested in genetic genealogy and 15pc do it for health reasons.
A person might only be doing a DNA test to find out how Viking they are, he says, but they should brace themselves for surprises.
"You could find out that your parents are not in fact your parents, or that you had a half-brother or half-sister you never knew existed. People need to be aware that surprises will happen, particularly when they are giving DNA tests as presents. They throw up unexpected results."
From her home in the state of Washington in the US, Alice Collins Plebuch set off on a remarkable journey of discovery when she started to explore what she assumed to be her Irish background. Her story is told by Copeland's The Lost Family. Plebuch sent away for a "just-for-fun DNA test" of the type that have now become commonplace.
She had been brought up to believe that both her parents were Irish-American Catholics, but she was still interested in filling in the gaps in her father's family tree.
When the DNA results came back, she was surprised to discover that while one half of her results confirmed a British and Irish background, the other half was European Jewish, Middle Eastern and East European.
Initially, she thought it was a mistake, but then she explored her father's background in depth. She described how she discovered that a cousin was not actually her cousin, and her dad's sister was not actually his sister.
Her father was not in fact related biologically to his own parents. Through DNA connections with a Jewish family who had found a similar discrepancy, Plebuch's mysterious background was found to be caused by a mix-up between two babies in a New York maternity hospital in 1913 just after birth. A Jewish baby had gone home with an Irish family, and an Irish child had gone home with a Jewish family.
Without DNA testing, this story would never have emerged. Close to 30 million people are thought to have recorded their DNA on a database with at least one of the four main consumer genetics companies. Copeland has predicted that due to DNA testing, the 2020s may turn out to be the decade that killed family secrets, for better and for worse.
This is mostly a positive development, she believes. "Even when people have a surprise about their own genetic background and that can be painful, they are usually glad to know," she tells Review. "That is not always true of the person who has maintained the secret. They are not always open to being contacted."
Susan Lohan, co-founder of the Adoption Rights Alliance, says the closed access to Irish adoption files means that DNA testing is the only option for many adoptees when it comes to finding out information.
Dolores Quinlan, who tracked down her birth mother through DNA two years ago, says those who are using the tests should be psychologically prepared for it.
She was adopted illegally as a baby in Dublin. She says she has a falsified birth certificate, listing her adoptive parents as her biological parents.
Quinlan stumbled upon the information that she had been adopted when she had a conversation with her father after her mother's death. She became suspicious that she had been adopted when he could not name the nursing home where she was born.
Suddenly at the age of 49, her whole identity was turned upside down when he confirmed she had been adopted through a GP.
When she tried to trace her mother through official channels, she was told that she would have less than a 5pc chance of finding her.
"I was supposed to die without knowing who my birth mother was, but I was not going to give up," she says.
Some who do DNA tests might have surprisingly quick results, but for Quinlan the process took two years, and initially there were no close matches.
"When you reach out, it's very frightening because someone could tell you to get lost.
But with the help of Gleeson, the genealogist, she was able to narrow down the search and wrote to one of her mother's sisters.
"It is something that you have to handle very sensitively, because I didn't want to shock my family," she said.
"When you reach out, it's very frightening because someone could tell you to get lost. I was psychologically prepared."
Fortunately, the response from her birth family was positive and she was rung up by her uncle, who said her mother in Drumcondra wanted to meet her immediately
"We have a lovely relationship," she says. "We have a lot of similarities and it wasn't like meeting a stranger at all. She couldn't believe it and she wondered if it was really happening. Her family say that I have enriched their lives and they have enriched mine."
As a psychotherapist, she cautions that not all of these meetings go well, and sometimes they change the dynamics in a family.
"Someone is used to being the oldest in the family and suddenly he finds out there is an older brother in Birmingham and he doesn't like that. These meetings are not always as exciting as they appear on television. And often a family has to come to terms with the fact that someone has kept a secret for all these years."
Meeting with a mother, father, son or daughter for the first time can be an emotional rollercoaster, she says.
"Intense feelings from the past as well as euphoria of finding each other can also turn to feelings of sadness and loss."
Theresa Hiney Tinggal is another woman who discovered she had been illegally adopted at birth and was determined to discover who her natural mother really was.
Having searched through DNA, she became used to the mixed responses when she contacted those with genetic family links. Some people wanted to help and others did not want to know.
"You send an email, and sometimes people reply and sometimes they don't, but eventually I tracked down my mother's family to Tipperary, and I was delighted.
"When I was looking for information from the authorities I hit a brick wall. I would never have found out who my mother was without DNA. To me, it's the best thing since sliced bread."
Are those using the DNA kits given enough psychological support to cope with surprises?
Quinlan says adoptees trying to find out information about their legal adoption might get the support of a social worker.
"When you are looking for information from DNA, you are often on your own."
Copeland says the DNA companies do escalate their customer service in sensitive cases, where unexpected relationships may emerge.
"The companies do warn people, but I don't know if you can prepare someone psychologically," she says. "DNA tests are complex. It's like spinning a roulette wheel. You don't know what you are going to find."
If you have had a similar experience with DNA testing and would like to share your story, please contact Kim Bielenberg at firstname.lastname@example.org